Bell 212A

The widely used protocols in Bell 212A modems are:

• Microcom Networking Protocol (MNP) Level 1-4: MNP enables error-free, asynchronous data transmissions. It was an industry standard in the 1980s.
• MNP Level 5: These protocols incorporate the first four levels along with a data compression algorithm. Due to their ability to compress data, these protocols can double the amount of data that can be sent at the modem's top transmission speed.
• V.42, V.42 bis: These protocols are internationally recognized for data compression and error control. V.42 includes Link Access Protocol and MNP 1-4. Two V.42 compliant modems use LAMP to control data errors between modems and retransmit bad data blocks. If one modem uses V.42 and the other supports MNP, they negotiate to use MNP protocol. In either case, the error control process is automatic and does not require any special software program.